jimbeetle - 8:07 pm on Oct 9, 2012 (gmt 0)
I'm pretty sure they use click through rate and bounce back rate on a per-term basis.
Over the past few days that's the only way I've come to believe G can use bounce rate. That and segmenting industries and sites into different buckets.
And here's where I think the "fresh boost" factor really plays a role: surface a new page then measure clicks and bounces.